Work in progress involves the isolation, purification and characterization of several lung proteases which appear to be involved to be involved in specific immunological injury in rabbit lung. Attempts will be made to localize these enzymes, utilizing two different approaches. One will involve isolation of highly purified preparations of different kinds of cells from normal and injured lung, and determination of their content of proteolytic enzymes. The second method will involve preparation of antibodies for each of the lung proteases isolated, and utilizing this technique with light and electron microscopy to determine the cellular and subcellular localization of these enzymes.